Since it has been found tht cisplatin [chemical name: cis-dichlorodiammine platinum (II)] has an anti-tumor activity [cf. Nature, Vol. 222, page 385 (1969)], there have been prepared many organic platinum complexes wherein various diamines are used as a ligand, and the anti-tumor activity of these compounds have also been studied. However, many of these known compounds show the anti-tumor activity against only a certain limited tumors and do not show sufficient anti-tumor effect. Further, although some of these known compounds show comparatively excellent anti-tumor activity, they have toxicity to kidney and the organ of hearing, or they have less solubility in water and hence are hardly prepared in a pharmaceutical preparation, or they are less easily transferred into organs in vivo [cf. Science, Vol. 192, page 774 (1976)]. Accordingly, most known compounds are not suitable for clinical use.
Accordingly, it has been desired to find novel organic platinum complex having excellent anti-tumor activity with less toxicity and with high water solubility.